1. Field of the Invention
The present invention relates to a method of manufacturing a metal matrix composite and a composition of the metal matrix composite.
2. Description of the Related Art
Metal matrix composites (MMCs) are composite materials that comprise at least two constituents, one being a primary metal and the other being a different secondary metal or another material, such as a ceramic article or organic compound. As compared to monolithic materials comprising a single constituent, MMCs have a higher strength-to-density ratio, a higher stiffness-to-density ratio, better fatigue resistance, and higher strength at elevated temperatures. MMCs also have a higher wear resistance than monolithic materials. As such, MMCs are typically useful for applications requiring wear resistance and strength, e.g., brakes.
MMCs are produced by augmenting the primary metal with the secondary metal or other material, which are typically some type of reinforcing material. The metals used for the primary metal and the reinforcing material are typically chosen to optimize the desired mechanical and physical properties of the MMCs. Numerous combinations of metals and reinforcing materials are known in the art. Examples of an effective metal as the primary metal are aluminum, magnesium, titanium, copper, zinc, and superalloys. Examples of effective reinforcing materials comprise boron carbide, silicon carbide, alumina, and graphite, and are available in the form of continuous fibers, discontinuous fibers, particles, and whiskers.
One method of producing MMCs includes impregnating or infiltrating a preform of the reinforcing materials with the primary metal. The preform is often a fabric or prearranged fibrous configuration of the reinforcing materials that is produced prior to metal infiltration.
Many existing preforms, however, suffer from fatigue and/or failure in non-reinforced dimensions and do not exhibit uniform strength in three dimensions. Additionally, existing preforms typically comprise small reinforcing materials, which enable consistent mixing during the formation of the preform. However, consistent mixing often becomes difficult as the size of the reinforcing materials decreases. Small reinforcing materials often limit the mechanical and physical properties, such as wear resistance, of the preform and in turn the MMCs.
Many existing preforms also exhibit inconsistent density as a result of inconsistent mixing. Since consistent mixing ideally includes both dispersion of reinforcing material agglomerates and uniform distribution of reinforcing materials throughout the preform and dispersion of reinforcing materials to prevent agglomerations, inconsistent mixing results in nonuniform distribution of reinforcing materials in existing preforms and contributes to preforms having inconsistent density, physical properties, and performance. Preforms having inconsistent density wear more readily and are not useful for applications requiring high wear resistance. Additional external reinforcing elements must often be added to existing preforms after formation to remedy these performance issues, which increases production costs of the MMCs.
Further, many existing preforms are heavy due to the required additional external reinforcing elements. Heavy preforms are often not suitable for applications requiring lightweight components, such as automotive or aeronautical applications.
Finally, many existing preforms suffer from weak points caused by entanglement and conglomeration of reinforcing materials. Preforms including entanglements and conglomerations do not exhibit sufficient strength and stiffness. MMCs formed from preforms including entanglement and conglomeration also suffer from inadequate metal infiltration due to blockages caused by such entanglement and conglomeration of reinforcing materials.
Due to the inadequacies of existing preforms and the method of manufacturing MMCs, there remains an opportunity to provide a preform that is easy to produce and light weight that meets the strength requirements of preforms used in metal matrix composites.